What is a before query Business rule?

What is a before query Business rule?
Before query Business rule is a special type of business rule in ServiceNow that is used when we want to limit which records can users access from a given table. While most of you would probably think that Contextual security Access control lists (ACL's from now on) are the default way to go, there are some drawbacks that stem from the way SN is built. In this article, we will discuss what options we have to secure our records, and in which use cases they are fit for purpose.

Example:

(function executeRule(current, previous /*null when async*/) {
     current.addQuery('name', '!=', 'Workingcode').addOrCondition('url',  '!=','https://www.workingcode.in/developer-forum/');
 })(current, previous);